Among the risks that an aircraft has to be able to deal with, there is a category of accidents designated by the expression controlled flight into terrain (CFIT). This category includes accidents during which an aircraft that is navigable under the control of its crew unintentionally strikes the relief, obstacles or a body of water without the crew being aware of the imminence of the collision.
To limit the risks associated with controlled flights into terrain, new monitoring instruments have been developed. Notable among these are the terrain awareness and warning system (TAWS). This system notably comprises a topographical database on the relief of the terrains. This type of system is totally effective only if the database notably contains topographical data that is consistent, accurate and exhaustive. The topographical relief data that feeds the systems of the terrain awareness and warning system type fully satisfies all these conditions.
However, quite the opposite applies when it comes to topographical data concerning obstacles (for example, man-made obstacles of electricity line type or even of very high construction type). In practice, the creation of a topographical database containing data on the obstacles with a level of accuracy that is acceptable for an aeronautical application requires accurate data to be collected for a large number of different obstacles distributed over geographic areas covering all of the earth's surface. Furthermore, how to collect and organize such information has not been defined by an independent organization.
Information on the obstacles can be obtained from various sources. However, collecting such heterogeneous and scattered data is a particularly difficult task. Furthermore, the accuracy and the quality of this data is difficult to guarantee and can vary considerably from one source to another.
There are also accessible and marketed databases containing topographical data for the obstacles. However, the accuracy of the data also varies considerably from one database to another. Furthermore, the way the data is structured is not necessarily optimized for the size, performance and reliability constraints imposed for an onboard aeronautical application.
This is why the topographical data concerning obstacles is not taken into account in the terrain awareness and warning systems, although its use can very significantly improve ground surveillance.